node-nfc-nci

NXP NFC NCI Linux Node wrapper

Install

npm install @vhs/node-nfc-nci

Note: See Requirements for installation requirements

Usage

const nci = require("node-nfc-nci");

This module exports an NCI interface object with single method: listen.

listen(callback: (context: EventEmitter) => void)

When called, listen will attempt to initialize the device (on a separate thread) via the embedded linux_libnfc-nci library and if successful, immediately call the callback with a context object.

The context object passed to the callback is an event emitter and enables asynchronous operations between reading tags.

See Events below for more information about the events. See Context below for more information about the context object.

Events

| Event | Argument(s) | Description | | ---------- | ------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | error | message<string> | emits on any error, even for errors when attempting to initialize the device. | | arrived | tag<Tag> | emits on NFC tag arrival | | departed | tag<Tag> | emits on NFC tag departure. Provide a copy of the original arrived tag. If NDEF data has been updated during the tag's presence it will not be reflected in departure. | | written | current<Tag>, previous<Tag> | emits on successful tag NDEF write. Provides updated tag and a copy of the original arrived tag prior to update. |

Objects and Interfaces

Context

Methods

context.setNextWrite(type<string>, content<string>)

Sets data to write for next tag to be detected.

This will attempt to indiscriminately write the next tag that arrives.

context.clearNextWrite()

Clears the pending next write.

context.hasNextWrite()<bool>

Check if there is a next write pending.

context.immediateWrite(type<string>, content<string>)

Attempts to immediately write to any device that is present. However, tag arrived event provides a tag.write function which is an alias of immediateWrite but likely more practical because immediateWrite depends on a device being present.

Tag Object

For properties, see example below.

Methods

tag.write(type<string>, content<string>)

This method attempts to immediately write to which ever tag is present.

As tag.write is a thin wrapper to context.immediateWrite, there are no guarantees that this write will only write to the tag specified in the tag object that was passed.

Acceptable types

• Text - writes en lang text to the NDEF content |

Example of a typical Tag Object payload

{
  "technology": {
    "code": 9,
    "name": "Type A - Mifare Ul",
    "type": "MIFARE_UL"
  },
  "uid": {
    "id": "04:e1:5f:d2:9c:39:80",
    "type": "NFCID1",
    "length": 7
  },
  "ndef": {
    "size": 868,
    "length": 18,
    "read": 11,
    "writeable": true,
    "type": "Text",
    "content": "hello world"
  }
}

Example

const nci = require("node-nfc-nci");

nci.listen((context) => {
    context.on("error", (msg) => console.log(msg));

    context.on("arrived", (tag) => {
        console.log(`ARRIVED: ${JSON.stringify(tag)}`);

        if (!context.hasNextWrite()) {
            if (tag.uid.id === "04:e1:5f:d2:9c:39:80") {
                tag.write("Text", "hello world");
            }
        }
    });

    context.on("written", (tag, previous) => {
        console.log(`PREVIOUS: ${JSON.stringify(previous)}`);
        console.log(`UPDATED: ${JSON.stringify(tag)}`);
    });

    context.on("departed", (tag) => {
        console.log(`DEPARTED: ${JSON.stringify(tag)}`);

        if (tag.ndef.content !== "foobar") {
            context.setNextWrite("Text", "foobar"); // will attempt write on any next tag
        }
    });
});

Requirements

As this module compiles and uses an embedded version of the library, installing this module only requires base development/build tools.

Alpine

sudo apk --no-cache alpine-sdk autoconf automake bash cmake libtool

Debian/Ubuntu

sudo apt install -y cmake automake autoconf libtool pkg-config